side_effect does not take a trailing "s", calling
side_effects will simply ignore the call and
continue. These test work because the no return
value are set, therefore the result is false.
Without changing the tests you can comment out
the try/except without breaking anything.
Fixing the tests shows that the call to
netifaces.ifaddresses was not covered for OSError
and test was missing for ValueError
Change-Id: I770390e99b4b614aff5512da11c0c226dc38b85f
512455da9e